Stable rocket propellant



STABLE ROCKET PROPELLANT Edwin F. Morello, Joliet, and Wayne A. Proell, Chicago,

111., and Norman J. Bowman, Hammond, Ind., assignors to Standard Oil Company, (Ihicag0, 111., a corporation of Indiana.

; Filed 912, 1955, Ser. No. 481,294 8 Claims. (01. 52 .s

vided carbon, desirably an aliphatic oxime, and a defined aromatic amine gassing inhibitor.

Ammonium nitrate is widely used as a component of high explosives, particularlythe so-called safe explosives.

Even though classified as a high explosive, ammonium nitrate is extremely non-sensitive to ordinaryheating and to shock and cannot be detonated readily by local application of heat or by a blasting cap. Furthermore, when ignited, ammonium nitrate does not burn uniformly and has a tendency to go out when used in the absence of combustible organic material. Thus, to rim prove the burning quality, to increase the sensitivity, and to utilize the excess free-oxygen made available by the decomposition of the ammonium nitrate, organic materials which also may function as binder material for the shaping of the ammonium nitrate into grains are ad mixed with ammonium nitrate. The choice of .components of binder material must be such that satisfactory combustion of the propellant grain with respect to burning rate under conditions of use can be realized.

1 2,942,962 Patented. June 28, 1960 the use of ammonium nitrate as the base material in solid propellant for rockets and ATO units quite attractive. -Moreover, the relative low flame temperature of the decomposition of ammonium nitrate (17302150 C.) makes desirable the use of ammonium nitrate. The

availability of free oxygen from the decomposition of the ammonium nitrate permits the use of oxidizable material in the binder material, the combustion of which enhances the energy available from the decomposition of the nitrate Certain characteristics of ammonium nitrate require development of suitable associated material in the composition to make ammonium nitrate suitable as a gas-generation means for rocket service or for take-offservice.

Solid ammonium nitrate exists in several difierent forms depending upon the temperature of the nitrate and in passing from one solid form to a different solid form,

particularly at temperatures of about 32 C and also '18 C. i.e., temperatures common to storage conditions, a considerable volume change takes place in the ammonium nitrate. Thusthe binder material used with the ammonium nitrate to formphysically stable grains must be flexible to compensate for changes in volume in order that such volume changeswill produce a minimum amount of voids and cracks in the grain. Moreover, the solid propellant grain suitable for military use must be ballistically stable after prolorigedstorage at temperatures ashigh as 77 C. and as low as about 60 C. Production of fissures inthe grain either internally or externally over the surface of the grain createsadditional burningsurface which results in unpredictability of the ballistic performance of the rocket or ATO unit. Thus itbecomes necessary toprovide a binder material which will provide ashaped grain of satisfactory physical stability. Furthermore, such grain must be capable of be- Modern warfare utilizes large quantities of rockets for ground-to-ground missiles, ship-to-shore missiles," airto-ground missiles, and air-to-air missiles. These rockets are comprised essentially of thin wall casings, which contain a combustion chamber in which is incorporated a quantity of solid propellant, a nozzle through which the decomposition gases pass thereby to create the forward thrust of the missile, ignition means for igniting the propellant grain, stabilizing vanes and a warhead which contains high explosive.v Military rockets heretofrom about 010 to 0.16 inch of propellantfgr'ain per second at about 1000 pounds per square inch pressure: The present invention is concerned primarily with propellant material for rockets, said propellant material having burning ratesabove about 0.16 inch per second at 1000 pounds pressure. Thus the burning rates desirable for'rocket service are higher than for take-off service although the rate of burning is below that of detonaf tion. 1

Such units are commonly :lmown as a in such take-off service are usually within therange of a ing ignited at extremely low or relatively high tempera.-- tures after being subjected to variable storage temperature conditions and to burn evenly and at such a rate as'to distribute the impulse energy in accordance with the, service required.

Finely powdered ammonium nitrate contains about 20% or more by volume of ,void space and this void space must becompletely filledin order to obtain a shaped explosive grain of thedesired physicalcharacteristics. Moreover additional void space is produced when using an. inorganic, compound, as the catalyst and the binder must not only fill the voids of the ammonium nitrate, but also the voids present in the finely powdered inorganic catalyst material. Another factor which contributes to the maintenance of uniformand smooth com bustion of the propellant grain is. that of stoichiometric oxygen balance for the production of water, carbon monoxide and carbon dioxide in the combustion of the propellant grain Hence, binder material, components capable of. furnishing a part of the oxygenfor combus tion of the grain are'used to supply any oxygen deficiency in the composition.

' characteristics of non-detonating explosives are depend Economic considerations of cost andavailabilhy make ent upon the temperature and pressurein the combustion chamber. Therelationship of burning rate and pressure at constant temperatureisexpressedbyR; N. Wimpress in Internal Ballistics of Solid Fuel Rockets (19S0), as

L 5*(1000) wherein B is thelinear burning rate at pressure pflfijis the linear burning rate forthe composition of 1000 p.s.i;;

' on log-log paper.

consists essentiallyof:

p is the pressure in p.s.i. in the burning chamber and nis the pressure exponent showing dependence of burning rate on pressure and is the numerical value equal to the slope of the curve of burning rate in inches per second Obtained by plotting the burning rate at various pressures Ammonium nitrate compositions usually have a pressure exponent of about 0.7 or higher. Smokeless powders, such as ballistite and cordite have pressure exponents between about 0.6 and 0.7. The lower the value of n the less is the detonating character-of the deconipositionof a.gas-producing composition and the more even and smooth is the burning rate of the propellant grain. Thus, a sustained thrust rather than a detonation is obtained by smooth burning ofithe grain.

f'ropellant compositions having an exponent less than about 0.65 are preferred and these propellant compositions for use in rocket service should have burning rates of at least 0.16 inchvper second at 1000'pounds pressure.

"One of the more serious problems in the use of ammonium nitrate base explosives as propellants lies in the tendency of the composition to produce gaseous deedinposition products in storage at extremely high atmospheric temperatures such as are prevalent in the tropic regions. This characteristic of ammonium nitrate base propellants is commonly known as gassing Military specifications require that this gassing tendency be held to a minimum. Many materials added tothe ammonium nitrate composition which increase the burning rate in crease the gassing tendency of the composition. Thls is particularly true with compositions containing finely divided carbon. Gassing is a very serious problem because grain compositions which have gassed" tocan appreciable extent'usually fail to give'satisfactory firings. This is believed to-be the result of increased porosity of the grain, which porosity causes uneven burning of the grain. Still more serious is the fact that grains which have gassed to a considerable extent tend to give erratic burning properties and even exhibit detonation properties.

An object of this inventionis the preparation of a gas generatingcomposition .for use in rockets, the principal gas-generating material of said composition being ammonium nitrate. Another object of the invention is the preparationof an explosive grainhaving a high burning rate which grain is dimensionally stable and non-fissuring oyera wide range of storage temperatures. Still another object of the invention is the production of anexplosive grain having a high burning rate and a moderately low pressure exponent, which explosive grain is suitable for 4 r sieve, preferably through a #200 U.S. Standard sieve and more preferably through a #325 U.S. Standard sieve;

(3) From about 10% to about 25% by weight of a plastic binder consisting essentially of: (a) Between about 18% and 40% by weight of cellulose acetate which analyzes from about 51% to 57% by weight acetic acid; and (b) From about 60% to about 82% by-weight of plasticizer components consisting essentially of: (i) The'liquid polyesterification condensation prod; uct'obtained by reacting "one mol of an aliphatic oxydicarboxylic acid containing'4 'to 6' carbon.

atoms per molecule with from about 1.08 mols to about 1.3 mols of at least one dihydric alcohol selected from the class consisting of'ethylene glycol, propylene glycol, polyethylene glycol ether, polypropylene glycol ether and mixtures thereof which ethers and mixtures thereof have an average molecular weight not more than about 200 "and which polyesterification condensation product is essentiallyanhydrous and has an average molecularweight of about 250 to about 1000.; and? (ii) At least one nitrodiphenyl ether containing from one tothree nitro groups per molecule'and substantially not morev than two'nitro groups on any benzene nucleus, theratio'by weight of. said .7

polyesterification condensation product (i) tosaid nitrodiphenyl ether (ii) in said binder being in the range ofl:4.to 4:l.- i.

(4) :From about 0.5 to 4% of a gassing inhibitor :se: lected from the class consisting of (a) v aromatic nucleusselected'from the class consisting "olj phenyl and naphthyl, R and R" are selccted from-the class consisting of hydrogen and alkyl containing from 1 use in military rockets. A stillfurther object of the invention is to produce an ammonium nitrate-combustible binder material grain which will ignite at relatively low temperatures and pressures. An additional object of the invention is to produce a combustible ammonium nitrate propellant grain, the pressure exponent of the burning attemperatures of about 135 C..

. lthas been discovered that an ammoniumnitrate based propellant grain of suitably high burning rate; suitably 19w pressure exponent,- and improved gassing tendency 1 An effective amount of a combustioncatalyst comprisingPrussian blue, generally from about 1% to about 8% by weight;

(2) From about 0.5% to about 7% by weight of finely divided carbon containing-not more than about 5% ash, the particle-size of; said carbonbeing such that the finely divided .carbomwillpass through a #2 0 US. Standard to 4 carbon atoms and x is an integer from 1 to 3; and (b) diphenylamine, dinaphthylamine, and phenyl naph thylamine.

(5) The remainder essentially all ammonium nitrate, said composition containing at least about 70% bygweight of ammonium-nitrate. r

To the above gas-producing propellant composition we prefer to add from about 1% to about 4% by weight of total composition an aliphatic 'oxime corresponding to the empirical formula ll ll R-C-(CHfl -C-R wherein R and R are selected from the class consisting of methyl, ethyl and hydrogen, wherein X is selected from the class consisting of oxygen and NOH and wherein y is an integer from 0 to 2.

INHIBITOR COMPONENT It has been discovered that certain aromatic amines when introduced into the ammonium nitrate based-grain containingPrussian blue catalyst and finely divided ear,

bon have the very desirable characteristic of decreasing the amount of gassing in high temperature storage and frequently even eliminating or essentially eliminating gasr.

sing for prolonged periods of time. In view of the. ex

'treme severity of'the test conditions for hot. storage sta bility, it is considered thatthe more elfective aromatic amine, dinaphthylamine and phenyl naphthylamineak-ln any reasonable storage time at atmospheric temperature storage conditions. v. The aromatic'amine gassing inhibitors of this invention fall intotwo main classes. These classes are: diphenylamine, dinaphthylarnine -and phenyl naphthylamin'e. In

. thecaseflof the naphthyl amines, theIinkage between the naphthyl radical and the nitrogen may be either alpha or beta. The sssonistq rsm t s;amia s whi hza In this empirical formula Z is an aromatic nucleus selected from the class consisting of phenyl and naphthyl; R is selected from the class consisting of hydrogen and alkyl containing from 1 to 12 carbon atoms; R and R" are selected from the class consisting of hydrogen, and alkyl containing from 1 to 4 carbon atoms; and x is an integer from 1 to 3.

Examples of monoamino-containing compounds are: aniline (monophenylamine, monoamino benzene), 1- naphthylamine, toluidine (methyl aniline) xylidine (dimethylaniline), dodecyl aniline, N-methyl aniline, N,N- dimethylaniline, N-sec-butyl aniline.

Examples of the diamino compounds are: diamino benzene (phenylenediamine), diamino toluene (toluene diamine), diamino naphthylene, methyl diamino naphthylene, ldodecyl diamino naphthylene, N-sec-butyl, diamino benzene; N,N-di-sec-butyl diamino benzene, and N-methyl diamino naphthylene. 1

Examples of triamino compounds are: triaminobenzene, triamino naphthylene, triamino toluene, and triamino methyl naphthylene. A distinct improvement in the gassing tendency of the composition is obtained by the use of very small amounts on theorder of 0.5% by'weight of the total composition. In general,,little additional benefit is obtained by the use of amounts of more than about 4% by Weight of the gassing inhibitor. In general, it is preferred to use from about 1% to about 3% by weight based on the total weight of the propellant composition of the invention.

CARBON COMPONENT Thecarbon component of the propellantgrain when used in amounts of from about 0.5 %.to about 7% by Weight of the grain increases the burning rate by about 0.01 to about 0.07 inch per second depending on the type and amount of carbon used. We prefer to use from about 1% to about 3% by weight of carbon in the composition Carbonin excess of about 7% is undesirable because the slight increase in burning rate is more than counterbalanced by thesmol iness imparted to the combustion gas stream.

The carbon component of the propellant composition which We add to increase the burning rate includes finely divided, highly adsorptive activated carbons. These are Well known in the art of decolorizing sugar and adsorption of gases. Examples of these are Norit and Nuchar, the former being a highly-adsorptive activated carbon used to adsorb odors, and to decolorize water, gases, chemical solutions, oils. and greases. Nuchar is an activated carbon made from a residual organic material obtained in the manufacture of cellulose and is characterized by high porosity resulting in high adsorptive capacity. Like Norit it is used as a decolorizing and deodorizing agent. i

A second general class of carbon useful for increasing the burning rate of the propellant composition are the carbon blacks. These are roughly classified as channel blacksprepared by the impingement of small natural gas flames, furnace combustion blacks produced by the partial combustion of essentially gaseous hydrocarbons in closed retorts and furnace thermal blacks produced bythermal decomposition of hydrocarbonssuch as acetylene in preheated furnaces. The carbon blacks are characterized by low, ash content by having extremely small particle size, that is, 50 to 5000 A., and contain adsorbed, hydrogen and oxygen. Other. carbon blacks which may be used ized by exceedingly small particle size, that is, well below #325 U.S. Standard sieve particle size. However, i to avoid dusting andconvenience in handling, some carbon blacks are formed to the so-called bead type carbon blacks which beads are generally of such dimensions as I to pass through a #20 US. Standard sieve and are retion is graphite, flake. and amorphous. If derived from a natural graphite, the ashcontent should. be reduced below about 5% which can be accomplished bytreating the natural product by air flotation or the ash content may be reduced by leaching with mineral acid or by other methods Well knownito the art.- We prefer graphite of colloidal or 'semi colloidal particle size.

Still another type of carbon which we have found effective for increasing the burning rate of the gasforming composition is finely ground petroleum coke, par-.

ticularly petroleum coke obtained as a. residue in the pipe-stilling of Mid-Continent heavy residuums. Such coke usually contains less than about 1% ash and is preferably pulverized to pass through a #325 U.S. Standard. sieve prior to incorporation in the gas-producing pro pellant composition. The coke may be activated by methods well known to the artto improve the-elficiency thereof as a burning rate promoter; in our propellantcomposition. i r

The carbon component of our composition contains not more than about 5% of ash and is. in afinely divided state. Particularly-suitable classes of carbons commercially available are activated carbon (active carbon or activated charcoal), carbon black, petroleum coke and graphite. In general, the finely divided carbon will pass through a #20, US. Standard sieve. Desirably more finely dividedmaterial is used, for example less than #200 US. Standard sieve size. It is preferred to use carbon having a particle size to pass through a #3 25 US. Standin the propellant-grains are lamp blacks produced by burningnliquid fuels such as petroleum oils, tars and aromaticresidues in specially designed pans, combustion taking place, under restricted air supply conditions. The carbonblacks as indicated above are generally characterard sieve or which is readily reduced to such a size dur-, ing the milling operation utilized in the preparation of the composition of the invention. Because of their uni. formity in physical characteristics and-their effectiveness, in raising the burning rate, the commercially available. carbon blacks are a preferred source of the carbon utilized herein. Activated carbons containing not more than about 3% ash are another preferred source of carbon for use herein.

The term ammonium nitrate -as used in this specifi cation and in the claims is intended to .mean either ordinary commercial grade ammonium nitrate, such as conventionally grained ammonium nitrate "containinga small amount of impurities and which is then'generally coated with a small amount of moisture-resisting material such aspetrolatum or paraffin, or military grade ammonia,

um nitrate, or a mixture of minor amounts of other inorganic nitrates such as sodium nitrate and/or potas V sium nitrate with the ammonium nitrate. Finely ground ammonium nitrate is preferred in order to reduce 'the voids to a minimum and hence avoidthe use ofex'css binder material. The shaped grain usually: contains at v than are theso'luble Prussian blues.

' cyanide complex, the catalyst may contain'alkali metal and/or ammonium ions. It has been found that the generic classes of iron-iron cyanide compounds known as the range of from about to 1:3. More usually, the

soluble Prussian blues andinsoluble Prussian blues are 7 effective catalysts for the purposes of this invention. It is known that the better soluble Prussian blues contain alkali m etal(s)' such as potassium and sodium and/or the ammoniurnradical. Some of the compounds which have been found to be effective area: ferro ferrocyanide, ferric ferrocyanide, ferro ferricyanide, ferric ferricyanide, potassium ferric ferrocyanide, sodium ferric ferrocyanide, ammonium ferric ferrocyanide, potassium soluble Prussian blue, sodium soluble Prussian blue and ammonium-sodi-. um soluble Prussian blue. 7

These applications show that the so called insoluble Prussian blues, either the chemical compound ferric ferrocyanide, or the commonly known insoluble Prussian blue,

are more effective catalysts at high pressure operation Thus when operating the combustionchambercontaining the solid propellant atlpressures between about 500 and 2000 psi.

a higher burning rate in inches per'second is obtainable 1 when using. a given composition containing insoluble Prussian 'bluejas the catalyst than is obtainable when using the same composition using soluble Prussian blue as the .catalyst. The insoluble Prussian blue containing explosive compositions are diflicult to ignite at atmospheric pressures when the amount of catalyst present islless than about 6' weight percent. However, these compositions ignite readily when an elevated pressure is imposed on the combustion'chamber prior to the application of the igniting means. 1

' The Prussian bluecatalyst is an essential component of the grain composition of this invention. It is understood that sufiicient Prussian blue is present in the grain to cause an undesirable amount of gassing in the high temperature test hereinafter described when the grain composition. contains finely divided carbon in addition to the cellulose acetate, nitrodiphenyl ether and polyester condensation product binder. In general, the presence of about 0.5 weight percent, on the total composition, of Prussian blue causes increased gassing.

, In addition to the Prussian blue, the grain composition ofthis invention may containother inorganic combustion catalyst,for example, the composition may contain one or more of the conventional chromium salt catalysts used for promoting the combustion of ammonium nitrate. These chromium salts which are utilizable as combustion catalysts include ammonium chromate, ammonium polychromate, alkalimetal chromate, alkali-metal polychrornate, ch'romic oxide, chromic nitrate and copper chromite. The' dischromates are the more effective catalysts and it is preferred to use ammonium dichromate.

. Copper oxide is another well-known catalyst for pro moting the combustion'of ammonium nitrate as is also ferric oxide. A

It is preferred in the composition of the invention to use one of the Prussian blues alone. However, for special situations it may be desirable to use-a mixture of Prussian blue and one of the chromium catalysts or. cupric oxide or f'ferric oxide. In general, the mixed catalyst willhave a weight ratio of Prussian blue to the other catalyst'in ratio is about 1:2. The prefered mixture consists of insoluble Prussian blue and ammonium dichromate.

In general, the compositions of the invention will contain-between about 1% and 8% by weight, on the total composition, and preferably from about 2% to about 4%.

v BINDER The hinder material of the gas-producing propellant composition consists essentially of cellulose acetate plasticized with:

; (a) The liquid polyesterification condensation product obtained by reacting an aliphatic oxydicarlz oxylic acid containing 4 to 6 carbon atoms per molecule with a din hydrical'coholyand I (b) At least one nitrodiphenyl ether containing from one to three nitro groups per molecule and substantially not more than two nitro groups .in any benzene nucleus.

The cellulose acetate used in this invention is known as a partially esterified cellulose acetate and .isd'escribed as having an acetic acid content between about 51. and I 57% by weight of acetic acid. The term percentby weight of acetic acid denotes the amount of acetic acid obtained on saponification of the cellulose acetate and is expressed as percent of the initial material. A particularly suitable cellulose acetate is lacquer grade, that is, a lacquer grade which analyzes between about 54 and 56% by weight of acetic acid. Lacquer grade cellulose acetate is described in addition to its acetic acid content by its viscosity, when dissolved in acetone, as between ahout 2 and centipoises at 25 C. Hereinafter,

the term viscosity as applied to cellulose acetate denotes the viscosity of an acetone solution containing 20% by weight of a cellulose acetate. The preferred cellulose acetate of this invention analyzes between about 54 and 56% by weight of acetic acid and has a viscosity within the range of about 2 to 10 centipoises. A binder having the propercharacteristics for use in preparing'the shaped explosive composition of this invention contains about 18 to 40% byweight of the defined cellulose acetate. Preferably, the bindercontains between about 18 and about'25% of the'defiled cellulose acetate.

The plasticizer utilized in the binder of this invention consists essentially of a combustion of two plasticizers, one of which is a liquid polyesterification condensation product obtained by reacting an aliphatic oxydicarboxylic acid containing 4 to 6-car bon atoms per molecule with an excess of, at least one dihydric alcohol selected from the class consisting of ethylene glycol, propylene glycol, polyethylene glycol ether, polypropylene glycol ether and mixtures of ethylene glycol ether with propylene glycol ether, which ethers and mixtures thereof have an average molecular Weight of not more than about 200. Poly"- ethylene glycol-200, which is a mixture of tetraethylene glycol and pentaethylene glycol which may contain a minor amount of triethylene glycol, but which mixture is predominantly tetraethylene glycol, may also be used asthc dihydric alcohol. A suitable aliphatic oxydicarQ boxylic acid for condensation with the polyhydric alcohol is diglycolic acid. Other oxydicarboxylic acids which -may be used are cxyacetic-propanoic acidand oxydif propanoic acid. We prefer to esterify diglycolic acid with ethylene glycol and the polyesterification condensation product is essentially anhydrous andhas an average molecular weight of about 250 to about 1000; The preferred polyesterification product obtained by reacting'ethcopendin-g'application of Norman J. Bowman and Wayne vA. Proell, -entitled Polyester Plasticizers, filed-November 30, 1954, Serial No. 471,992, nowfabandone'dffMol ratios of dihydricalcohol to thei' -oxydica'rboxylic acid en rance in the polyesterification reaction mixture are preferably within .the range of from about 1.l-l.25 toLO. In preparing the polyesterification product the oxydicarboxylic acid is dissolved in the dihydric alcohol and the solution is heated, preferably in a 2-stage thermal treatment, the first stage being carried out at temperatures below about 150 C. and in the final heating stage temperatures within the range of from about 150 C. to about 200. C. are used. The extent of polyesterification is controlled by adjusting the factors of time, temperature and pressure at which the polyesterification is carried out and at least 70% of the water theoretically producible for complete esterification for the alcohol-acid charge is withdrawn. The amount of water withdrawn from the polyesterification mixture during the heating thereof is used as a measure of the progress of the polyesterification to completion. The heating of the reaction mixture is usually for a total time of at least six hours up to thirty hours or more. At least a partof the final heating stage may be carried out under reduced pressure conditions, Essentially anhydrous polyesterification products are produced, the average molecular weights of which products depend:

1) On the mol ratio or dihydric alcohol to. oxydicarboxylic acid in the solution introduced to the polyesterification reaction zone; 7

(2) On the extent of completion of the polyesterification reaction as indicated from the amount of water withdrawn from the reaction zone; and

(3) On the molecular weigh-ts of the dihydric alcohol and the oxydicarboxylic acid introduced to thepolyesterification reaction zone. Preferably, the reaction is carried out to not less than 80% completion as based on the water theoretically producible. The term water theoretically producible? as used herein is defined as two mols of water per mol of aliphatic oxydicarboxylic acid charged to the polyesterification reaction zone. In general, the greater the excess of dihydric alcohol used in the reaction mixture, the higher is the percent completion of the reaction. Thus, for a -mol percent excess dihydric alcohol in the reaction mixture, the reaction is carried out to 85-95% completion and when 30 mol percent excess dihydric alcohol is ued, the esterification should be carried out to 90l0O% completion.

The other plasticizer component of the binder is a nitrodiphenyl ether, preferably nitrodiphenyl ether containing as an average about two nitro groups per molecule although nitrodiphenyl ethers containing from one tothree nitro groups per molecule may be used. Substantially not more than two nitro groups are present on any benzene nucleus, and as an average less than about 2.5 nitro groups per molecule of nitrodiphenyl ether are present when a mixture of nitrodiphenyl ethers is used.

We prefer to use as the second plasticizer component 2,4-dinitrodiphenyl ether which may beprepared in high yields by reacting phenol with 2,4-dinitrochlorbenzene as describedin copending application of Wayne A. Proell and Norman J. Bowman entitled Thermoplastic Compositions, filedOctober 27, 1954, Serial No. 465,132. Mixtures of nitrodiphenyl ethers may be prepared from diphenyl ether by methods well-knownin'the art, using either fuming nitric acid or mixtures of concentrated nitric acid and concentrated sulfuric acid asnitrating agent. Commercial productsconsisting of amajor proportion of diphenyl ether and a minor proportion of diphenyl may be used as the intermediate for nitration in the preparation of the nitrodiphenyl ether plasticizer component of this invention. DowthermAf which is a eutectic mixture containing about 73.5% diphenyl, ether and' 26.5% .diphenyl is such a commercial product and may be used for the production of mixtures comprising mononitrodiphenyl ethers with dinitrodiphenyl ethers and mixtures of trinitrodiphenyl ethers with these nitrodiphenyl ethers containing less nitro substituent groups than trinitrodiphenyl ethers; The termhnixtttr'es of mononitrodiphenyl ether anddinitrodiphenyl ether and mix tures of the foregoing with trinitrodiphenyl ether and in general, the term nitrodiphenyl ether is used in specification and in the claims to include nitrodiphenyl ether and mixtures of nitrodiphenyl ethers produced from 'Dowtherm A. Such nitrodiphenyl ethers will contain of -from.about,18 to about 40% by weight of the cellulose. acetate and from about 60% to about 82% by weight of theplasticizer components. The ratio (by weight) of the polyesterification condensation product plasticizer to nitrodiphenyl ether plasticizer inthe binder is within, the range of from about 1:4 to 4: 1. We prefer about equal percentsby. weight of these two plasticizers in the binder material.

OXIME COMPONENT As indicated hereinabove, We prefer a gas-forming propellant composition containingan aliphatic acyclic oxime which is added to the binder composition for the purpose of irnproving the combustion characteristics of the grain material with respect to the pressure exponent. The amount of oxime incorporated in the gas-producing composition is from about 1% to about 4% by weight of the composition and preferably between about 2% and 3%. Oximes corresponding to the formula as defined above are preferred. Examples of such oximes are acetonylacetone dioxime, acetylacetone dioxime, acetonylacetone monoxime, and succinaldehyde dioxime. These oximes are particularly effective for depressing the pressure exponent of the defined explosive composition with which they are associated and are also effective in promoting ignitability of the compositions at extremely low temperatures. The oxime component is added to the molten binder material prior to the addition of the nitrate, catalyst and carbon or may be added during the milling operation to which the ammonium nitrate and binder are subjected in completing the fabrication of the grain composition.

Acetonylacetone monoxime and acetonylacetone dioxime may be prepared by reacting in stoichiometric pro ture and dried after washing with a small amount of water. Acetylacetone oximes may be prepared in similar manner using acetylacetone intermediate.

In preparing the compositions of this invention, the binder material is first prepared, the oxime being then thoroughly mixed with the bindenafter which the ammonium nitrate, carbon and catalystaremilled with the binder. The binder is prepared by heating the plasticizer material at a temperature notin excessof about 150 C., usually within the range of from about C. to about 14 0? C. Theheated'plasticizer material, that is, the mixture of polyesterification condensation product, for example ethylene glycol'diglycolate, and, nitrodiphenyl ether, is stirred and the cellulose acetate is added, heating and stirring being continued until a ho mogeneous mixture is obtained. The oxime is then added to the mixture and is thoroughly mixed therewith before the addition of the thoroughly mixed ammonium nitrate, carbon and the catalyst components of the finished grain. The catalyst may be added, mixed with a part of the ammonium nitrate or it may be added immediately precedm'onium nitrate, carbon-and catalyst are then milled into the vplasticized mass at a temperature below about 120" C. andpreferably at'a temperature of about 110 C. If desired, the carbon may be added and milled with the plasticized binder containing the oxime (where oXime is a component of the grain) before milling the ammonium nitrate and catalyst into the composition. Milling is continued until ,a product of uniform texture .is obtained. Burning rate test strips are extruded or molded under pressure and the material is shaped into propellant grains as describedhereinbelow.

The rate of burning of the grain material 'is determined at jdifferentpress'ures in an inert atmosphere. The test gstrandsao'f ,materialsfor the determination of buming r'jates oficompo'sitions herein described were prepared by ramextrusioniat about 110 C. The procedure outlined below describes the preparation of the gas-producing'propellant compositions the results of burningtests of which are givenI in Tables 1 and 2 below.

' PREPARATION .OF PROPELLANT COMPOSITIONS A-miXture of 3464 parts by weightVof,2,4-dinitrodi phenyl ether and 34.64 parts by weight of ethylene glycoldiglycolate, prepared accordingto the procedure described 'hereinabove, was added and stirred at, a-temperatore-within the'range ofp120-140 C. to obtain a homogeneousmixture of theplasticizer material. To this mixture was added a" total of 20.72 parts by weightof cellulose acetate (LL-1 lacquer grade) which analyzed between 54 and 56% by weight of acetic acid. The cellulose acetate was added in small portions during the stirring of the plasticizer and when all of the cellulose acetate had become plasticized as indicated by a-homogeneous moltenrproduct, the molten product was colled to the range of'1l5'-120 C. and 1 parts by weight of acetonylacetonedioxime was added. The oX-irne was incorporatied in the plasticized mass'by rapid stirring to form a'homogeneous binder including the oxime. These 100 parts by weight constituted 23% by weight of the total graimcomposition and the binder components of these 100 parts, that is, 90 parts, constituted 20.7% of the total grain composition. 7

The ammonium nitrate used in fabricatingthe gasforrning propellant materiaL-the' performance of which is described in the table s, Was a commercial grade. Samplesof this ammonium nitrate (as received) were divided .into'70 and-30% portions'and the" 70% portionwas ground at 14,000 r.p.m., in a pulverizer to such a size that it would pass completely through a #325 U.S. Standard sieve. The ammonium nitrate (as received) was of such particle size as to pass'substantially completely through a-qt 325 U.S.'Standard sieve. The ground material was recombined with the unground material and thoroughly mixed therewith to give ammonium nitrate of small parti'clef size; at least 75% of which would pass through a #325 'U.S.-Standard sieve.

The ammonium-nitrate was then divided'into portions of one third and two-thirds ofthe total ofarnrnonium nitrate to'- -be used in the-grain. The finely'divided car bon black-inan aniount of from l to o f the total grain composition-and the insoluble Prussian blue cata' .lyst'werethen thoroughly admixed with the one-third portion ofthe ammonium nitrate to ,be used, The binder material containingjthe oXime .was stirred at,.*1j10 to 120 C.-in a sigma; blade mixer. The one-third portion of ammonium *nitrate'containing the carbon and Prussian blue catalyst-were then added rapidly and the mixture .was milled *for from .15 to 12 0 minutes, the temperature "of themixture .beingln' raintainedjbetween about 110 and 120C. At lthe end' of this 15-20 minute period"the mercury. Homogenization was complete at the end' of this milling period. I i

The amine inhibitor may be added to the, liquid binder prior to the addition of the ammonium nitrate; this" is desirable when theinhibitor is a liquid. Or, the inhibitor may be mined into the ammonium nitrate prior to intro? duction into the binder; this method is more commonly usedwhen the inhibitor is a friable solid. 7

Burning rate test strips of the above material were formed by subjecting the material contained in a 1 di ameter cylinder to 2,000 pounds pressure and extrudingfl therefrom through janaperture a strand of about diameter. Thecompositionofthis invention flowsfairly v with fresh materials to produce satisfactory grains." The reworkabilityof--r,ejects results in asubstantjal saving over conventional grains where rcjects cannot {be Ire worlged. The material was maintained ,ata temperature of about C.v during the ram extrusion Oflthe strand. A-fte'r made to a timing device. The timing device was started by the fusing of one wire and as the testpieceburned along its lentgh thetirning device was stoppedby th 'fusing of the second wire. Thus the' time]or' the burning of the three inches of the test piece wasobtained. The test piece was ignitedby means of a Nichrome resistance Wire place in sn a w t one a f. t t st p e Burning rates for. the test pieceswvere. determined at pressures 019 600, 8100, 1'O00, 1200, 14-00, 1600, and 1800 pounds persquare inch. of nitrogen pressure. Burning rate in inches per second torthe difiierent pressures was p do Q :1 g..paP 1 .9 e h t i hilin relationship. The islope' of this line is defined as the pressure exponent of the burning rate. .Bur .ning ratescf thematerials'in this specification are definedas'bnrning a s 000.ri undsa mse .p e r n h epa tion. '.sh r s ant a n g the gas-forming material the hot mass was loaded into a I 2% '5 diameter mold, maintained atatemperature of about 110 C. Temperatures above about 120 C. are avoided in'the milling and molding of the ammonium nitrate-con,-

. taining, grainin order to minimize the possibility otheat ignition of thefcomposition .under conditionsxot milling and molding. g'Ifhemold in which the material is loaded is providedwith aninset which maybe of one or u ore diiferent'shapes. Tius the inset proyi des.thegrainwith 1 he forrn of afcross,gstar, trie itudin l spam. anglev or oth' carp Ede. 1111i 9 m1Y dis ihumd i raalg ur us u -J The g a n m r/If be'tuh iormasillustrated' V ernoided-intohdisceshapedg preierably pe'rforated ,for' use inrockets and missiles.

Discs ,of theamaterial' ar e' jsuitably, SPEl'cedin the rocket caseltqprovidejnniform combustioirof the discsliapcd grains. ,In molding the material into grains subjected". to. 10,000 .p.s.-il ram ,pressuregfor gabputjiive minutes fqiftcr yidgdchL lthe .ram' pressure, was; reducd to emanate h reem e ma ntaine "fe aui m k w s the fmoldl The, propellant press and allowed to cool to room temperature The grain was removed from the mold and cut to 4" lengths.

The exterior surface of the grains was inhibited to presevere temperature changes in order to determine the resistance of the grain to fissuring. In this test,-"the grain was placed in a cabinet for a period of two hours, which cabinet was maintained at a temperature of 80 C. At the end of the two-hour period, the grain was removed and placed in a cold cabinet maintained at a temperature of '60 C. for a period of two hours. This complete cycle of extreme temperature change was followed immediately by a secondcycle wherein the grain was again subjected to the temperature of 80 C. for'two hours followed by a two-hour period in them 60 C. cabinet. Following this two-cycle temperature treatment, the grain waspermitted to come to room temperature after which it was examined for external fissures and the condition of the internal structure of the grain, with respect to fissures, wasdetermined by testing the grain in a miniature rocket motor. The grains so cycled showed no variation, with respect to burning properties, from similar grains which had not been subjected to the temperature cycling tests.

' The grains prepared as described above were tested for burning properties in a miniature rocket motor. This motor consisted'essentially of a cylinder closed atone end and threaded at the open end. The straight side of the cylinder was about 8 inches long and the cylinder had an internal diameter of about 3 inches. funnel-shaped portion provided with an opening for theattachment of a nozzle Qand'provided with threads at the larger end was threaded onto; the cylindrical casing to complete the cornbustionchamber of the motor. Various sized orifices wereprovided in order to permit the operation of the motor at different combustion cham ber pressures. inch in diameter. By varying the orifice size the com-. bustion chamber pressure could'be. varied from about 700 to about 2000 p.s.i. fie

In the combustion of a grain containing no internal fissures the pressure at the initial stage of the combustion rises rapidly to a level within the range of from about -700p.s.i., to 1000 p.s.i., andremains atsuch level without appreciable variation during'the combustion of the entire grain. Any irregularities such as fissures in the grain, internal or external, cause irregular fluctuation in the pressure developed by the combustion ofthe grain.

.In order to reduce the amount of explosive material needed per motor test, a perforated cylindrical aluminum slug was used to take up about half the longitudinal volume of the motor. Thus in operation the motor contained the slug and a 2.5 inch diameter perforated grain 4 inches long.

The grain was ignited by a black powder mixture,

which mixture was in turn ignited by means of an electrical squib. It was found that satisfactory ignition jcould be obtained by using 25 g. or the following mixturei'sparkler powder, 10 g.; FFG= gun powder,"7.5 gl;

and FFEG powder, 7.5 g. This mixture was placed at the jlno zzle end of the funnel shaped member and was held. in place means of a paper disc pressed firmly against the slopingsides "of the member. The motor was, assembled by inserting'into the casing first the aluminum slugand then the grain tobetested. The test V p 14 end complete with powder ignite'r was 'then screwed to the casing. The electrical squib was then inserted through the nozzle opening until it contacted the powder mixture. This method of arming the motor is particularly desirable because the motor is essentially inert 'until a few seconds before the test run is fired. It has been found thatthis method of ignition gives ignition delays between about 100 and 500 milliseconds e It is to be noted that the presence of ash -in the carbon has littlefor no effect on the' efliciency of the carbon for increasing the burning rate until the percentage reaches a figure above 5.0% ash. Thus graphite with an ashco ntent of 3.52% increased the burning rate at 1% amount onlyabout 14%.. Nuchar whichhad an ash content of about 5% likewisewas reduced in efiiciency with respect to increasing the burning rateof the; composition. The data with respect to channel blacks and furnace blacks indicate that samples ofthe latter which contained about 5.0% ash were of elficiency equal to the-channel blacks, none of which contained more than about 0.15% ash. The compositions which contained 2 .30 oxime exhibited low pressure exponents. Tests on various grain compositions consisting of the defined binder components, various types of finely divided carbon as defined herein, insoluble Prussian blue catalyst and mixtures of'insoluble Prussian blue and ammonium 'dichromate were compared with the same compositionscontaining various of the defined amine inhibitors., Itwwas found that the presence of the amine in 0.58to 0.64. Theseburningrates and pressure exponents These;' orifices varied from 0.17 to 0.24

make these compo'sitionsfsuitable'forLuse in rocket pro. pelled missiles as well as'in ATO units wherein high burning ratesare desired.

' HIGH. TEMPERATURE STABILITY TESTS .The' results obtainable by the addition of. the defined airlines to the composition consisting of the defined binder, insoluble'Prussian blue catalyst or mixtures of catalyst and finely divided carbon are set out below. The gassing tendency was measured byan arbitrary test which has purposely been made more severe than anything that would be imposed on the composition at atmospheric temperatures. This test is commonly designated as C. Gas Stability Test. This test is carried out as follows: i

Three gramsof a finely divided ammonium nitrate base composition are placed in a vessel. The vessel is connected by tubing to a mercury manometer system which is so arranged'that differential readings of the manometer are translatable'into volume changes in the system. Since the-volume change of the sample itself can bedisregarded, thevolum'e change in the system corresponds to the amount of gaseous decomposition products of the sample. The vessel is inserted to an opening in a metal block; thismetal block is provided with electrical heating. elements and controls which permit the block to be maintained 'at .a temperature of 135 ceriti: grader A periodof 15 minutes is allowed for the sample to come to the temperature of 135 C. At this timethe manometer is 'zeroe'd. Readings are taken at 15 minute intervals until suflicient readings have been taken to indi cate that the gas product rate is substantially consistent i.e., has reached an equilibrium value or the gas product rate is so low that the sample obviously has more than satisfactory low gassing tendency. The manometer readings are converted directly to cc./'g./hr. ,for each 15 minute interval. The gas rate in cc./g./hr. foreach 15 minute interval is then plotted against'the time of heating of the sample. This rate is hereinafter written as cc./g./hr. i i

In the results reported hereinbelow, the rate of gassing hereinaboye.

.lar weight in therange of, from about 350 to about 600.

- fa e with, e e en ee ne n 11e presen e of s dium is setout a ne our, two hou s and h e hours. w e f the heating was continued for thatlengthof'time; and also the maximum rate of g'assingfand the time at'whi ch the maximum rate was reached. It has been found that some compositions have a hump in the curve and the, maximum gas rate is higher than the long-term equilibri- In general, it is considered that a composition which has a zero gassing rate during the first hour of heating (essentially zero means :within the limit .of error ofthe t s wh h i o t e o de fo ,s-/ i l substantially tree .of gassing tendency in storage at atmospheric temperatures. l It is considered that a compositign which has a gassing tendency not in excess of about 2 cc./g./ hr. at the first hour of heating at a temperatureof 135 has a s atistactory gassing tendency with respect to hot storagesi e 'at temperatures as high as 77 CQ fo'r aperiodfoi 0' days. (Tests showjliat compositions consisting of the defined I binder, Prussian blue catalyst and ar'r'r'moniumlnitrate, while exhibitinig appreciable gassing are jof satisfaetorygassing tendency. The presence of finely divided carbon in thiseomposition markedly accelerates 'the gas product and renders such acomposition unsatisfactory witli respect to storage stability at atmospherictemperatures.) l s i arie A rate of gassing at the end of the first hourof heating and this maximum is particularly high atfl-l-ccLofi' -ga's ing qualities of the material; when fabricated in grain form, is not substantial. We have foundthat theihigh gassing rate maximum occurring in the early stages of the heating-period, that is, the surge'of gas from the fA number of amines were tested for gas inhibition effectiveness in' a control composition which had 'arather high maximum gas ratel' Thec'ontrolsamp'le; that is,

the sample containing no-amineadditive had 'the following P 2 ifi i V ingredient:

' ,flmmoni nn 'nitrate...

Insoluble Prussian blue,"

- Norite .;A .actiyatedcarbon 0.8 0

' Carbon black L;.' 10.20

Binder:

/ Cellulose acetate 4.76

= E yl n l ol digl ole p l 2,4-dit1itrodi'phen'Yl eth Acetonyla'cetone d H v,

The ammonium nitrate ofthe composition was a. commercialgrade. ammoniuminitrate, of which.70.% of .the sample was ground in a micro-pulverizer' at 14000 -r.p.m., the vremaining :being 'un'ground ammonium nitrate. At least .75% 'of...the,-ammonii1m, nitrate was of ,such particle .sizeaasuto p'asssthrou'gh a ,#325. US. Standard sieve. The carbon was of particle size to pass through a #325 U '.S.-.Standard; sieve,and contained 3.27% ash.

The carbon blackflcontained no ash, was of particlesize to pass througha #325 US. Standard sieve. The cellu lose acetate of the binder was a lacquer grade analyzing between 54 and 56% by ',weight ,of acetic acid. T he ethylene glycol diglycolate. component of the binder was the, polyesterification p oduct Obtained by reacting 'digly- .colic acid with ethylene glycol prepared as described Theproduct was liquid and had a molecu- F h ;'lArd itnd n ny e er c mpon nt was f hig P ri y n a p pare by. .Ieaeting '2, i itr e benzene with phenol as describedhereinaboye. .j'Ihe ,acetonylacetone dioxime component of the'propellant mat ia Pr pa by. re t ns' hydrexyl mmon um s 1- droxide and water as described ,hereinabove. V .In,-preparing the samples tor the tests the results of w ha fs i Tab L1 0 pa sb We Oft above composition were pu lyetized in the mortar and ,enoughamine added ,to have 2. ,by weight present in t oug l iXe i h fiqm sitiq r gri d n d E PE asnife m ma u ,h heeapbta n d- The results of these tests are set out in Table Lrthe matte} samplesontainingneoaimeindicat dam i n m heating'ofthe sample was inaugurated, whichrateawas t to a i hib t d .wtn s t en The am n wa :with respect to gassing of the composition which c the mixed catalyst, that is, reduced amount of inso ,Prussian blue catalyst; and 2) he -fayorable efiect ;of

material, is indicative of possible impaired burning prop- V rIn still another test, the propellant grain composition containing no carbon and no oxime was testedlwith respect togassing properties, that is, a controbsample and the same composition containing of--thegdiphenyl amine was examined. The control sample contained 74% of the ammonium nitrate,'-8-.05% cellulose-acetate, 5.75% ethylene glycol diglycolate, 9.2% ;2,4-dinitrodiplienyl ether, and3.0% insoluble Prussian bluecatalyst. This control sample containing no oximeho-carbonand no' amine stabilizer established 'agassingrate of of gas per gram per'hour within a fewminutesi fier maintained for the three hour period of the-test. This composition has a gassingtendency low enoughgto. meet military requirements of high' temperature storage stability. The addition of 2% by weight'of diphenyl .amine to this composition resulted in a material whichshowed a uniform maximum rate of 0.5 ccugas per' gram-. per hour after one hour of heating at C.

Test Series c In addition to the above tests, the effect of usinga mixed catalyst was investigated. Thus, the 3% insoluble Prussian blue catalyst was substituted with a catalyst consisting of 1% insoluble Prussian blue'and 2 o 'mmoniu m dichromate with and withou'tfthe pre nee f aminestabilizer. The control sample and the "a me stabilized sample had compositions'tabulated below:

(Control sample showed no gassing at the end of, hour,"a rateof 1 cc. per gram per hour/at the two ,stage of .the heating and a rate are] cc. 'of g'as" per; per hour atthe end of threehours. The sample 'wh ch had been stabilized with diphenyl amine show'edgio gassing for a period of- 6 /2 hours, with a: gassing ratejof 1.90 cc, 0f gas, per gram per a "hours." This'test illustrates: (1) the. reduced.

wdiphenyl .am n n stab i t m si ie e llen is quite low. b

, i 1f g thoughthe tendency to gas in the absence of the amine 'Test Series D In still another series of tests, the eifect of omitting the oxime from the composition was examined. The

composition of the control sample and of the sample containing diphenyl amine are tabulated below.

identical composition containing ,the N,N-diethyl anilinejstabilizer, instead of the diphenyl amine was also tested. Omission of the crime from these, compositions showed very little. eifect o n the' gassing properties. Thus the control sample containing no oxime and no amine stabilizer showed a uniform gassing rate of only 3 cc. of gas per gramper hour .over the period of four hours heating. This rate was reached almost immediately after the sample was brought to equilibrium temperature, i.e., 135 C. The composition containing the 2% of diphenyl amine showed zero gassing for a period of 2% hours, with a rate of 4 cc. per gram per hour at the three hour heating time and the maximum rate of 5.6 cc.; per gram per hour at the end of four hours. The sample .containingthe N,N-diethy1 aniline did not gas until heated for a period of about 3 hours when the rate was 0.8. cc. per gram per hour. This sample reached a maximum rate of 4.3 cc. per gram per hour in about 5% hours. The gassing, rates of compositions containing no the unit is made: up of. a tubular member. 11 which is closed at one endand which is provided with threads at they open end. Member 11 is provided with two loops, 12. and 13. These loops are used to, hang the unit from a carrier, not shown, which is attached to the. wing'of the aircraft. This carrier makes it possible to jettison the unit after take-ofi. A somewhat funnel shaped member one end of the grain-will be inhibited toypreventcombustion. I i i Although a tubular grain is illustrated herein, the invention is not limited to, such a grain. Anytparticular shape may be utilized. Examples of other shapes are cylinder, cruciform, triform, hexaform, octaform and slab as described above. In the case of perforated grains, the

perforation may be .circularor star-shaped with various numbers of pointsin the star.- Furthermore, a singly cylindrical grain having one or more longitudinal perfo rations may be utilized in some cases, instead of the multigrain unit shown. 1

b The grains are held in longitudinal position and prevented by sliding back f and forth in the combustion chamberby means of a wire grid 26. Wire grid .26 consists of a ring out to fit the threads of member 14 and provided with a grid worl; of metal wires that willresist the high temperature existing in the combustion chamber.

. On one side of the conical portion of member 14 there is-provided 'for the combustion chamber a saretywemn means 28. Venting means 28 comprises aftulnilar mem 'ber fastened to member 14, which tubular member-has full access to the combustion chamber and is provided with a rupture disc, not shown. Therupt-ure disc iser such construction thatexcess pressure in'the combustion chamber will blow out the disc, whereby the pressure in the combustion'chamber will be held below thepointiof serious damage to the 'unit. f A An igniter means is positioned within memberg14 sozas to close oil the nozzle 16.. The igniter meansconsists. of a container 31 filled with .black powder, or some other easily ignited material, which can produce a large volume of gases at elevatedpressure. 1 A"'s quib L321fbr igniting the powder, is attachedto'thecontainer lilfin communica tion with the powder ,c'ontainedjtlierein. Electrical wires 33 connnect a Wire in the'sq'uib' tothe electrical systemof the aircraft and-a switch therein, (the connections to the aircraftare notshown). b Q

The ATO unit is assembled as follows: The grains are inserted into member 11. fVenting means 28? are fastened to member 14. Igniter 3 1 isinseited through the large open end and fitted so as to close the nozzle, the wires 33 having first been passed through the nozzle 16.. The

wire grid 26 is screwed into the large'operi end of member 14; The assembled nozzle portion is the'n securely screwed onto member 11. ff f,

The assembled unit is then attached to the wing of the aircraft by loops 12 and 13; wires 33 are connected to the electrical operating assembly in the aircraft. When the 14 is attached to memberll by engagement of the threads 1 r at the large open end of member 14 with the threads on member 11. Member 14 is provided with a nozzle 16 through which the decomposition products pass. The size of nozzle 16 determines in part the pressure maintained inside of the chamber formed by members 12 and 14.

The solid propellant fills the cylindrical portion of member 11. The solid propellant in this illustration consists of seven tubular grains, 17, 18, 19, 20, 21, 22 and 23; each having an CD. of about 3 inches and having a centrally located cylindrical opening 1 inch in diameter, the full length of the grain; the grains are approximately 30inches long. The grains used herein consist essentially of Prussin blue catalyst, which may be insoluble Prussian blue catalyst, diaminotoluene binder, oxime,

carbon and ammonium nitrate as described for grain Each grain has the annular area at each end inhibited pilot desires to obtain the assistedtake-ofl, -he throws the switch which causes the currentto pass through wire 33 and to heat up the firing wire in squib 32, which inturn ignites the powder in the container 31. b j

The containeris of suificientlstrength to withstand the initial pressure generated by thegases from the powder. The hot gases raise the pressure in the combustion chamber high enough to permit the grain to ignite. The combustion of the grain causes the pressure in the chamber to rise to a point which cannot be resisted by container 31. The container disintegrates and the pieces are discharged through nozzle 16. The total time from throwing the switch to full operation of the unit is on the order of less than 0.5 second.

As the gases pass out of the nozzle the reaction acts on the aircraft and adds its thrust to assist the aircrafts propeller; a marked increase in forward speed results and permits the aircraft to take off in a shorterspace of time p or it permits lifting a load heavier than could be airborne by the use of the propellers alone.

When using about 4%. or more of the iron-type catalyst, the grain will ignite at relatively low pressures and no special precautions are necessary to maintain elevated pressure in the chamber until ignition occurs, as shown above. In this case, the igniter may be introduced into the combustion chamber by a means attached to the conigel.

cal portion of member 14 (this procedure is conventionally While the invention has been illustratedby an assisted.

take o'fB-operation it is probabl'e'that the pneferred use Will -be inair-to-aii missiles:- l

.co.fnositionofniattet.suitablefor use. s a p consis ing: f an efteetiveantount of a combustion catalyst.comprising Brussian bluegftom about 0.5%. to asthma y; weightof, finely dividi mrbon containing not mote than. about ash. the narticlle size of. said carbon being such that the finely diyidedcarbonwill pass througha #v Standard sieve.v from about 10% qabo t .125 by weight 'of; a plastic. binder consisting ssen i lly 015 between about: 1834a and. 40%. by w igh f c llulose acetate which. analyzes from. about 5.1% to 57% by ht aeetielacid; andf dm about. 6 toabout. 82% yli nlasti'cizer. comnonentsconsisting essentially of he; liquid pdb' stexification. condensation. p oduct ob mined by reacting one mol of an aliphatic oxydicarboxr ylie-lacid containin 4 to,v c rbo natoms Per: mo with ftomiabout 1.0.8 tools. to. about 1.3. mols. of at least one dihydric, alcohol. selected from. the class consisting of ethylene glycol pnopylene. glycol, polyethylene. glycol ether, polypropylene glycol. ether and mixtures thereof which. others and mixtures. thereof have an. average molecular weight not more. than. about 200 and. which polystetification. condensa ion product. is. essentially n yoatme-ocotamzooomwoob V 29 to about 1000; and at least one nitrodiphenyl ether. con: taining from-one to three nitro groups permol'ecule and;

substantially not more than two nitro groups on any ben zene nucleus, the ratioby weight of said polyesterification condensation product to said nitnodiphenyl; et-heit in said binder being in the range. oi 1:45 to 4.111;; from about 0.5.1v to 4.% of a gassing; inhibitor selected fromthecl'ass: consistingof (a) RZ( N-RR.")x. where- R isselected: from. the class consisting of hydrogen and alkyl containing froml to 12 carbon atoms, Z is an aromatic nucleus selected from the class consisting of phenyl and: naphthyl, R and R"';arc selected from the class consisting of hydrogen and tially all ammonium nitrate,- said compositiomcontaining; V

at least about 70% :by weight. of ammonium nitrate.

2. The composition of claim 1- wherein said. combustion catalyst is present in an. amount. between. about 1%.- and about 8% by weight.

3. The. composition ofclaiml wherein said cotnbusi tion catalyst is insoluble Prussian" blue.

4. The composition of claim l'wherein $3ld' inhibitor is diaminotoluene.

5. The composition o f 'claim lflwh erein said inhibitor.

is diphenylamine. I I V v 6.. The composition as described in claimfl containing from about 1% to about 4% by weight'ofsaid compo? formula sition, an aliphatic oxime corresponding to the empirical wherein R and- R are selected from the class; consisting of methyl. ethyl and hydrogen, X is selected from the class: consisting of oxygen and NOH, and y is an integer fror'nO'to- 2; V a

7: The composition of clai' '6. wherein the oxime is acetonylaoetone dioxime. I 1 I 8. 'A- shaped gas-producing propellant grain composi tion' consisting oi a':) about 4.75 70' by weight ofcellulose acetate which analyzes 54% to 56% byweight of'acetic acid, ('b) about '8%- by weightof f 2',4'dinitrodiphenylether, (b) about 8%-- by: weight of the anhydrous. liquid polyesterification condensation 'product ofethylene glycol with diglycolic acid, said condensationproduothaving-an average molecular weight within the rang'e of about" 3 to about 600,"(:d) about-3% by weight of insoIublePrus= drone and has. an avetese: moleculat weight. of. about 250 Noretetenceecited. 

1. A COMPOSITION OF MATTER SUITABLE FOR USE AS A PROPELLANT CONSISTING OF AN EFFECTIVE AMOUNT OF A COMBUSTION CATALYST COMPRISING PRUSSIAN BLUE, FROM ABOUT 0.5% TO ABOUT 7% BY WEIGHT OF FINELY DIVIDED CARBON CONTAINING NOT MORE THAN ABOUT 5% ASH, THE PARTICLE SIZE OF SAID CARBON BEING SUCH THAT THE FINELY DIVIDED CARBON WILL PASS THROUGH A #20 U.S. STANDARD SIEVE, FROM ABOUT 10% TO ABOUT 25% BY WEIGHT OF A PLASTIC BINDER CONSISTING ESSENTIALLY OF BETWEEN ABOUT 18% AND 40% BY WEIGHT OF CELLULOSE ACETATE WHICH ANALYZES FROM ABOUT 51% TO 57% BY WEIGHT ACETIC ACID, AND FROM ABOUT 60% TO 82% BY WEIGHT OF PLASTICIZER COMPONENTS CONSISTING ESSENTIALLY OF THE LIQUID POLYESTERIFICATION CONDENSATION PRODUCT OBTAINED BY REACTING ONE MOL OF AN ALIPHATIC OXYDICARBOXYLIC ACID CONTAINING 4 TO 6 CARBON ATOMS PER MOLECULE WITH FROM ABOUT 1.08 MOLS TO ABOUT 1.3 MOLS OF AT LEAST ONE DIHYDRIC ALCOHOL SELECTED FROM THE CLASS CONSISTING OF ETHYLENE GLYCOL, PROPYLENE GLYCOL, POLYETHYLENE GLYCOL ETHER, POLYPROPYLENE GLYCOL ETHER AND MIXTURES THEREOF WHICH ETHERS AND MIXTURES THEREOF HAVE AN AVERAGE MOLECULAR WEIGHT NOT MORE THAN ABOUT 200 AND WHICH POLYESTERIFICATION CONDENSATION PRODUCT IS ESSENTIALLY ANHYDROUS AND HAS AN AVERAGE MOLECULAR WEIGHT OF ABOUT 250 TO ABOUT 1000, AND AT LEAST ONE NITRODIPHENYL ETHER CONTAINING FROM ONE TO THREE NITRO GROUPS PER MOLECULE AND SUBSTANTIALLY NOT MORE THAN TWO NITRO GROUPS ON ANY BENZENE NUCLEUS, THE RATIO BY WEIGHT OF SAID POLYESTERIFICATION CONDENSATION PRODUCT TO SAID NITRODIPHENYL ETHER IN SAID BINDER BEING IN THE RANGE OF 1:4 TO 4:1, FROM ABOUT 0.5 TO 4% OF A GASSING INHIBITOR SELECTED FROM THE CLASS CONSISTING OF (A) RZ(NR''R")X WHERE R IS SELECTED FROM THE CLASS CONSISTING OF HYDROGEN AND ALKYL CONTAINING FROM 1 TO 12 CARBON ATOMS, Z IS AN AROMATIC NUCLEUS SELECTED FROM THE CLASS CONSISTING OF PHENYL AND NAPHTHYL, R'' AND R" ARE SELECTED FROM THE CLASS CONSISTING OF HYDROGEN AND ALKYL CONTAINING FROM 1 TO 4 CARBON ATOMS AND X IS AN INTEGER FROM 1 TO 3, AND (B) DIPHENYLAMINE, DINAPHTHYLAMINE, AND PHENYL NAPHTHYLAMINE, THE REMAINDER ESSENTIALLY ALL AMMONIUM NITRATE, SAID COMPOSITION CONTAINING AT LEAST ABOUT 70% BY WEIGHT OF AMMONIUM NITRATE. 